The single crystal (SC) castings of superalloy DD419 were prepared by using seeds deformed in different degrees. The grain structure on the etched seed surface and on the longitudinal sections was examined, combined with the measurement of the corresponding crystal orientation, in order to identify the origin of the stray grains. On the surface of the light-deformed seeds, only slightly?recrystallized?grains were detected, which had no influence on the SC growth of the superalloy castings. In the moderately and severely deformed seeds, however, recrystallized?grains in different degrees were observed. It was deduced that the recrystallization on the surface of deformed seeds occurred during preheating and holding stage, which was very similar to the recrystallization structure formed during the conventional solution heat treatment. These recrystallized grains were partially melted in preheating and pouring stage. In the subsequent solidification process, stray grains grown epitaxially from the unmelted residual recrystallized grains near the remelting interface. The experimental results show that the origin of the stray grains during seeding process is the recrystallization in the seed surface layer, instead of the nucleation of the new grains ahead of the melt-back interface.